It is important for elastomeric copolymers that are used in tires, hoses, power transmission belts and other industrial products to have a good compatibility with fillers, such as carbon black and silica. To attain improved interaction with fillers, such elastomeric copolymers can be functionalized with various compounds, such as amines. It has also been recognized that carbon black, when employed as reinforcing filler in rubber compounds, should be well dispersed throughout the rubber in order to improve various physical properties.
EP 0 316 255 A1 discloses a process for end-capping polydienes by reacting a metal terminated polydiene with a capping agent such as a halogenated nitrile, a heterocyclic aromatic nitrogen-containing compound or an alkyl benzoate. Additionally, EP 0 316 255 A1 discloses that both ends of the polydiene chains can be capped with polar groups by utilizing functionalized initiators, such as lithium amides.
U.S. Pat. No. 4,894,409 teaches a rubber composition comprising not less than 20% by weight of an amino group-containing diene based polymer in a rubber component, and 10 to 100 parts by weight of silica as a filler with respect to 100 parts by weight of the rubber component.
U.S. Pat. No. 4,935,471 A discloses methods of synthesizing living anionic polymerization initiators based on aromatic N-heterocyclic compounds such as pyrrole, imidazole, pyrazole, pyrazinyl, pyrimidine, pyridazinyl and phenanthroline derivatives and their use in the production of N-functionalized polybutadienes. A similar approach is disclosed in U.S. Pat. No. 6,515,087 B2, EP 0 590 491 A1 and WO 2011/076377 where acyclic and cyclic amines are used in the preparation of the active anionic polymerization initiators and are utilized in a further step in the synthesis of di-N-functionalized butadiene-styrene copolymers.
The synthesis of di-N-functionalized butadiene-styrene polymers is also disclosed in U.S. Pat. No. 4,196,154 A, U.S. Pat. No. 4,861,742 A and U.S. Pat. No. 3,109,871 A. However, in the processes for their preparation, aminofunctional aryl-methyl ketones are used and also serve as functionalizing terminating agents. The above described N-modification methods only allow the preparation of polydienes in which the polymer chain may contain no more than two moieties with amine functionality.
Another approach to prepare N-functionalized polymers with a different content of N-functional groups would be the incorporation of suitable styrene monomers into the polymer chain, which controlled addition into the reaction system would lead to a wide variety of styrene-butadiene rubbers with a different content of N-functional groups and thus exhibiting different ability to disperse inorganic fillers. EP 1 792 892 A2 discloses a method for the preparation of N-functionalized styrene monomers (by the reaction of a variety of acyclic and cyclic lithium amides with 1,3- or 1,4-divinylobenzene, 1,3-di(iso-propylene)benzene or a mixture of isomeric chloro-methylvinylbenzenes) that are used in a further step in the preparation of butadiene-styrene copolymer rubbers containing different amounts of amino-functional groups.
According to U.S. Pat. No. 6,627,722 B2, polymer-containing units of a vinylaromatic ring-substituted with one or two alkyleneimine-alkyl groups, especially pyrrolidinylmethyl or hexamethylene-iminomethyl groups, can be polymerized into elastomeric copolymers having low hysteresis and good compatibility with fillers, such as carbon black and silica. Improved polymer properties are achieved because the styrene derivatives improve the compatibility of the rubber with the fillers.
EP 2 772 515 A1 teaches a conjugated diene polymer obtained by polymerizing a monomer component including a conjugated diene component and a silicon-containing vinyl compound. The silicon-containing vinyl compound may be a silyl-substitued styrene. However, the compounds according to EP 2 772 515 A1 are hydrolytically unstable under the typical processing conditions, compare the N,N-bis(SiMe3)2 aniline derivatives disclosed in Org. Lett. 2001, 3, 2729.
Therefore, it was the object of the present invention to overcome the disadvantages associated with the prior art and to provide functionalized styrene derivatives whose application in the synthesis of polydienes leads to end-chain and/or in-chain modified polymer compositions that have better affinity to both of the two typical fillers commonly applied in tire production, i.e. silica and carbon black. The functionalized styrene derivatives should also be hydrolytically more stable than those of EP 2 772 515 A1.
This object was achieved by the use of [bis(trihydrocarbyl-silyl)aminosilyl]-functionalized styrene derivatives of formula (I). These styrene derivatives are preferably used as co-monomers in the production of elastomeric copolymers. Alternatively, or additionally, they are preferably used in the preparation of polymerization initiators.